How to make a character class/FPS loadout system

I need to know how to make a character loadout and class screen for my FPS game.

I would suggest following the tutorials on UMG, they go over creating an inventory system that you could probably change to suit your needs. - YouTube

You might also want to look at enums/switch on enum while controlling your enum state elsewhere in the blueprint (essentially a little state machine). That’d be one way I’d approach setting classes and load outs. And like Laurens said above, check the UMG tutorials on inventory.